Defining the Issues: Supernovae Saul Perlmutter Berkeley
Premise #1: Dark Energy, after 10 years, is still…
Premise #1: Dark Energy, after 10 years, is still... “Right now, not only for cosmology but for elementary particle theory, this is the bone in our throat .” — Steven Weinberg “Maybe the most fundamentally mysterious thing in basic science.” — Frank Wilczek “Would be Number 1 on my list of things to figure out.” — Edward Witten “This is the biggest embarrassment in theoretical physics.” — Michael Turner
Premise #2: After 10 years... supernova measurements still provide the best developed and tested technique, and yield the best constraints to date on the Hubble diagram and the dark energy equation-of- state. …And these measurements can be taken much further in precision and redshift. (Other days this week we will discuss the crucial need for, and strengths of, the other measurement methods, but for today’s discussion we will be working to carry through on this bedrock method.)
For this meeting’s SN working sessions: Describe and discuss the missing elements for the next big step in SN precision: measurements, instrumentation, empirical and theoretical understanding, and analysis tools. What does this imply for the space-based and ground-based planning?
For this meeting’s SN working sessions: What are factual elements that we can agree on 1 that set the parameters of these programs? What calculations or compilations can be performed to establish them? What are the decisions in defining these 2 programs that must be based on science “taste”? Are there any changes in circumstances or data that would influence these preferences?
For this meeting’s SN working sessions: What are factual elements that we can agree on 1 that set the parameters of these programs? What calculations or compilations can be performed to establish them? If we can begin to compile these questions, and come to agreement on these factual issues/calculations over the next months, the field will be ready to work together — particularly if/when there is an opportunity for a joint Europe − U.S. mission.
50 The Union Compilation of SNe Ia — the world’s data set so far 45 arXiv:0804.4142 μ 40 Miknaitis et al. (2007) Astier et al. (2006) Riess et al. (2007) Knop et al. (2003) (SCP) Barris et al. (2003) Tonry et al. (2003) Perlmutter et al. (1999) (SCP) Riess et al. (1998) + HZT This Work (SCP) 35 Jha et al. (2006) Riess et al. (1996) Krisciunas et al. (2005) Hamuy et al. (1996) 0 0.2 1.0 2.0 z
We can go beyond the indicators of stretch SN diversity we currently use to calibrate SN luminosity.
B SNe Ia are not “ all over the map ” : V There are lightcurve “ twins ” R I
SNe Ia B are not “ all over the map ” : There are lightcurve “ twins ” V
The twins are not rare. The 6 examples of lightcurve B twins shown on this and the preceding slides were drawn from a sample of 35 V SNe.
SN1992A, Day 0, Δ m 15 = 1.31 ± 0.02 Spectroscopic Twins Similarly there are many spectroscopic “twins” SN1992bl, Day 1, Δ m 15 = 1.29 ± 0.17 SN2002el, Day -4, Δ m 15 = ? SN1998bu, Day -2, Δ m 15 = 1.13 ± 0.05 SN1994D, Day -3, Δ m 15 = 1.46 ± 0.02 SN2001el, Day 1, Δ m 15 = 1.15 ± 0.04
Foley et al (2005) Moreover, spectra can be matched from low ‐ redshift to Low Redshift high ‐ redshift and over different High Redshift epochs on the lightcurve.
So it should not surprise us that we can use further lightcurve and spectroscopy indicators to show both diversity and consistency (and thus calibrate). but: Generally these are based on studies of just nearby SNe so 1) cannot yet use these indicators to limitation improve cosmology measurement, and fr om gr ound 2) until recently (with SNfactory providing nearby Hubble ‐ flow SNe), no relative luminosity calibration was possible because of peculiar velocity.
Spectral indicators: line ratios R Ca R Si
These subgroups also seen in preliminary Lightcurve indicator: SDSS data with larger sample. rise time Strovink (2007) apparently clusters into two subgroups flux rise time time (days)
Nearby SN Factory: Bailey et al, arXiv:0905.0340 Accepted for publication Spectroscopic Standardization 6% distance accuracy from a single spectrum Hubble Residuals R 642/443 R 642/443 +color SALT2 R 642/443
Wang et al (2009): Spectroscopic Feature Identification of “Dust” R V
Mark Phillips (Santa Barbara, 2009):
Mark Phillips (Santa Barbara, 2009):
And we can even correlate with the “Stretch” and Environment Sullivan et al. host galaxy environment. (2006) “Young” Star- forming galaxies “Old” Passive galaxies Stretch � Fainter/faster SNe Brighter/slower SNe �
It appears that we can greatly improve statistical uncertainty, and the constraints on systematics such as evolution but: Most of these indicators require limitation measurements than we cannot obtain fr om gr ound from the ground at even moderately high redshifts.
“Dust” is currently one of the most challenging aspects of the measurement. Scare quotes around “dust” because it appears that using color we are probably calibrating something more intrinsic to the SNe than the usual dust.
“Dust” is currently one of the most challenging aspects of the measurement, because: We do not have good constraints on the intrinsic color of each SN. We do not have high ‐ precision color measurements over a wide wavelength range. limitation fr om gr ound
With second, bluer color, U − B , the SNe show a color ‐ color locus that does not follow a CCM dust law (for a wide range of R B ). This indicates that intrinsic color is another parameter.
Sullivan et al. 08 The color vs. Extinction Hubble ‐ residual Vector Residual from Hubble line plot similarly indicates that the SNe are not following just a CCM dust law.
Even if one has identified the intrinsic colors of the supernovae the current color measurements are insufficient to constrain the “dust.” Uncertainty in Color Measurement Redshift
Even if one has identified the intrinsic colors of the supernovae the current color measurements are insufficient to constrain the “dust.” Uncertainty in Color Measurement Redshift
Even if one has identified the intrinsic colors of the supernovae the current color measurements are insufficient to constrain the “dust.” Uncertainty in Color Measurement and multiple color measurements are needed over a wide wavelength range. tar get uncer tainty Redshift
A definitive SN experiment must obtain the same set of measurements at every redshift.
A definitive SN experiment must obtain the same set of measurements of SN and host galaxy at every redshift i.e., a homogeneous dataset
…i.e., the same restframe wavelengths at every redshift F o r e xample , to use the se spe c tral fe ature indic ato rs e ve ry SN must be o bse rve d o ve r the se re stframe wave le ngths. Color calibration needed over the observed wavelength range. R Ca R Si SiII
Same set of SN measurements over what redshift range? From first principles: Measure expansion history out to the redshifts at which dark energy is no longer expected to be a significant component.
Redshift range
Redshift range 0.2 Ω m = 0.27, w 0 = -0.93, w a = 0 Ω m = 0.27, w 0 = -1, w a = 0.6 Magnitude difference from a flat, Ω Λ = 0.7 model 0.1 SNAP binned 0 double exponential potential pure exponential (fine tuned) a l -0.1 n t i t e p o i c o d e r i p inverse tracker S U G R A p o t e n t i a l potential -0.2 0.0 0.5 1.0 1.5 2.0 z (based on Weller, Albrecht 2001)
For this whole redshift range, study every SN in the same restframe wavelengths.
For this whole redshift range, study every SN in the same restframe wavelengths. What restframe wavelengths?
What restframe wavelengths? 0.3 to 0.63 mic ro ns inc lude s o ve r 90% o f the SN light and is the wave le ngth range whe re SNe have primarily be e n studie d.
What restframe wavelengths? …T his also c o rre spo nds to the wave le ngth range whic h give s a distanc e mo dulus fit at the 0.15 mag le ve l, whe n we fit A B and R B to ac c o unt fo r c o lo r. distance modulus uncertainty target uncertainty (mag) maximum wavelength of range Wave le ngth range : fro m 0.3 mic ro ns to 0.63 mic ro ns
What restframe wavelengths? …And this also c o rre spo nds to the wave le ngth range whic h c apture s the main spe c tral fe ature s that have be e n studie d as abso lute magnitude indic ato rs. R Ca R Si SiII
Do we need visible ‐ wavelength detectors? For what redshifts can these standard restframe wavelengths be studied from the ground?
At what redshifts can these wavelengths be studied from the ground? redshift F r om the gr ound these wavelengths can only be studied up to z ~ 0.5 or 0.6 atmospheric emission wavelength (microns)
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